This invention relates generally to fuel supply systems and more particularly to fuel supply systems for automotive vehicles that are installed in a fuel tank that tilts during vehicle operation.
The packaging constraints of modern passenger vehicles require shallow, large platform fuel tanks. Fuel sending units which may include a fuel pump, are located in these fuel tanks for optimal packaging rather than for optimal fuel pickup at all tank attitudes. Consequently, there is a need to maintain fuel in the vicinity of the fuel sending unit at low fuel levels when the fuel tank tilts as a result of vehicle maneuvers and unlevel attitudes. Traditionally, this need has been met by providing a small reservoir inside the fuel tank that contains the fuel pickup of the fuel sending unit. The reservoir fills to the nominal fuel level in the fuel tank when the fuel tank is level and keeps a quantity of fuel in the vicinity of the fuel pickup when the fuel tank tilts and the fuel outside the reservoir flows away from the fuel pickup.
This reservoir may attached to the bottom of the fuel tank or it may be attached to the fuel pickup portion of the fuel sending unit. The quantity of fuel retained in the reservoir is necessarily small when the reservoir is attached to the fuel pickup due to the sending unit access hole size. Since the quantity of retained fuel is small, the time of vehicle operation before running out of fuel is limited especially when operating the vehicle on grades.
A large reservoir can be attached to the bottom of the fuel tank to retain more fuel and provide a longer operating time when the fuel tank is tilted. However, installation of a larger reservoir requires either a two piece fuel tank or a very large access hole and means to attach the reservoir to the bottom of the tank.
The tank capacity for a given packaging space is optimized by using a one-piece, blow-molded, contoured fuel tank of thermoplastic material. Thus the use of a two-piece fuel tank is not desirable because it sacrifices tank capacity and further because it costs more to manufacture. On the other hand, a large access hole is difficult and expensive to seal. Thus a larger reservoir attached to the bottom of the fuel tank also leaves something to be desired.
It has also been proposed to accommodate fuel tank tilt by providing conduits inside the fuel tank that lead from peripheral locations in the fuel tank to a selector valve that is inside the fuel tank. See for instance U.S. Pat. No. 2,239,098 issued to Frank B. Hunter Apr. 22, 1941; U.S. Pat. No. 2,831,490 issued to William Harold Simcock Apr. 22, 1958; U.S. Pat. No. 2,934,077 issued to James Clifford Whiting Apr. 26, 1960 and U.S. Pat. No. 4,878,511 issued to Clarence D. Fox Nov. 7, 1989.
However, the fuel supply systems disclosed in these patents pick up fuel at only two remote locations near the bottom of the fuel tank that are on opposite sides of the fuel tank. Consequently these fuel supply systems can only accommodate fuel tank tilt about one horizontal axis, such as tilt fore and aft about a lateral or y-axis. Moreover, these patents do not disclose any feasible method for assembling the fuel supply system inside a one-piece fuel tank.